This invention relates to compressed-gas-operated devices of the reciprocating-piston type. The invention is particularly although not exclusively applicable to percussive tools such as pneumatically-operated concrete breakers, rock drills, chipping hammers and the like.
In such devices a piston is caused to reciprocate in a cylinder and to do useful work during or at the end of its forward working stroke, for example by impacting against an anvil or the shank of a tool bit. In order to achieve reciprocation of the piston, compressed air or other pressure fluid medium has to be directed alternately to opposite ends of the cylinder so as to move the piston. This operating fluid is usually conducted through longitudinal passages formed in the wall of the cylinder. The usual method of construction of these cylinders has been by casting or forging out of high quality case-hardenable steel or cast iron, and subsequently machining the main cylinder bore and the fluid transfer passage(s). This method of construction results in a component which is both heavy and expensive.
One object of the present invention is to provide a compressed-gas-operated reciprocating-piston device having an improved construction of cylinder component, which is used in conjunction with a surrounding tubular muffler and produces an improved sound-attenuating effect on the exhaust gas discharged from the device in operation, as well as on the general operating noise.